What is the position of oldest secondary phloem ?

Options

A. Just outside the pericycle
B. Just outside the vascular cambium
C. Just below the pericycle
D. Below the vascular cambium

Answer

To determine the position of the oldest secondary phloem, we need to understand the structure of the vascular system in plants, particularly during secondary growth. Here’s a step-by-step solution:

### Step-by-Step Solution:

1. **Understand the Types of Phloem**:
- There are two types of phloem: primary phloem and secondary phloem. Primary phloem is formed during the primary growth of the plant, while secondary phloem is produced during secondary growth.

2. **Role of Vascular Cambium**:
- The vascular cambium is a layer of meristematic tissue that is responsible for the production of secondary phloem and secondary xylem. It is located between the primary phloem and primary xylem.

3. **Location of Secondary Phloem**:
- After secondary growth, the secondary phloem is produced outside the vascular cambium. As new layers of secondary phloem are formed, the older layers are pushed inward.

4. **Position of Oldest Secondary Phloem**:
- The oldest secondary phloem is not located outside the pericycle or just outside the vascular cambium. Instead, it is found just below the pericycle.

5. **Conclusion**:
- Therefore, the correct answer to the question is that the oldest secondary phloem is positioned just below the pericycle.

### Final Answer:
The position of the oldest secondary phloem is **just below the pericycle**.

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